Wood-sealing composition



Patented May '2, 1939 PATENT OFFICE WOOD-SEALING COMPOSITION Melvin W. Johnson, Nutley, N. J., assignor to Pittsburgh Plate Glass Company,

County,

Allegheny Pa., a corporation of Pennsylvania No Drawing. Application November 12, 1937, Serial No. 174,155

5 Claims.

The present invention relates to the staining and sealing of relatively porous materials such as wood or the like.

One object of the invention is to provide a combination stain and sealer compound which when applied to bodies containing different types of wood will produce a relatively uniform color, Without unduly obscuring the natural grain of the wood.

A second object of the invention is to provide a combination stain and sealer material for coating wood which is permanent in color and which will penetrate the pores of the wood to a sulficient degree to inhibit exposure of unstained wood upon accidental rupture of the surface coating.

These and other objects will be apparent from consideration of the following specification and the appended claims.

In the coating of porous bodies, notably those composed of wood, it is common practice to apply to the surface to be coated a tinted filmforming solution .of nitrocellulose which forms a more or less transparent film of desired color tone upon the surface and closes the pores thereof without unduly obscuring or hiding the natural grain of the surface. Subsequently one or more coatings of a conventional varnish or lacquer may be applied over the sealing coating. The sealing materials. usually contain in addition to nitrocellulose, a gum, a plasticizer, a coloring agent and a suitable solvent for nitrocellulose. The sealers are classified according to the coloring agents employed in them. One type containsan aniline dye of suitable color and the second type is colored by a suitable pigment. Dyes and pigmentary coloring matters may also be combined in a single composition.

The first of these compositions tends to a certain degree to penetrate into the grain of the wood to which it is applied, thereby incorporating the color so that upon chipping of the surface coating complete exposure of the. uncolored wood does not result. However, the dyes employed in staining the solution are not always as permanent as might be desired. Moreover, the penetration of the dye into woods of different types is not uniform and therefore when bodies are composed of-a plurality of different woods, it is difiicult, if not impossible, to obtain uniform staining action.

Staining and sealing compositions containing pigments do not penetrate the grain of the wood so readily as materials which contain a dye as the coloring agent. Therefore, the staining action with different types of woods is more uniform in character. However, this failure to penetrate is often objectionable because upon accidental chipping of the coating unstained wood is left exposed. Moreover, the pigments tend unduly to obscure the natural grain and often where the latter is unusual or of ornamental character this obscuring is objectionable.

The present invention involves the provision of a combination stain and sealer composition which substantially combines the good points or both types of sealer and staining material heretofore employed without incorporation of the disadvantages inherent in either. Briefly stated, the invention involves the discovery that certain semi-drying oils, notably rape seed oil, may by suitable heat treatment be transformed into a base for sealer compositions which is of excellent and permanent color, which provides a substantially uniform coloration, even where the surface to be coated comprises a plurality of woods of different types, and which penetrates the grain of the wood to a sufiicient degree to obviate exposure of unstained wood in event of surface chipping.

Rape seed oil for treatment in accordance with the provisionsof the present invention may be either raw or preoxidized. It has been found that upon heating this oil to a temperature of about 600 F. for a period of about 2 to 4 hours the oil will assume a beautiful yellow tint admirably simulating maple. The period of heat treatment may vary over a considerable range, for example, from 2 to 4 hours. Operating tem peratures are fairly critical, because lowering of the temperature substantially below 500 F. is likely to result in failure to develop the desired color in the oil. On the other hand substantial raising of the temperature above about 650 F. is likely to cause decomposition and insolubility of the oil. A satisfactory test for determining when the treatment has progressed sufficiently,- far involves comparison of the tint of a 70% solution of the oil in xylol with a 40% solution of gilsonite selects in xylol. Test tubes of A inch diameter may be employed in making the tests. When the colors of the two solutions are approximately the same treatment is complete.

' Rape seed oil when so treated does not require the addition of dyes or pigments, and may be formulated into various sealer compositions. The following constitute specific examples of such materials:

Example No. 1 Pounds Nitrocellulose 2.5 011 base 10 Resin 5 Zn stearate 1 1 Toluol; j J 60 Butyl acetate 21.5

Example No. 2 Pounds Nitrocellulose 8 Oil base 10 Resin 13 Zn stearate 6 Toluol 40 Butyl acetate 23 Example No. 3 Pounds Nitrocellulose 5 Oil base 20 Toluol 40 Ethyl acetate 15 Butyl acetate 20 I 100 In the examples nitrocellulose may be any conventional type of nitrocellulose, for example, of a viscosity ranging between A and 20 seconds. The oil base of course is the rape seed oil which has been treated in accordance with the provisions of the present invention. The resin embodied in Examples 1 and 2 may be any conventional resin, such as ester gum, copal, alkyd resins, or other resinous material which is compatible with nitrocellulose. Zinc stearate constitutes a fiatting agent and may as shown in Example 3 be omitted. It may also, if desired, be replaced with other conventional fiatting agents. The toluol and the ester solvents may be replaced by other conventional solvents anddiluents.

The sealer coat or coats usually receive one or more coats of varnish or lacquer. However, such coats may be omitted if so desired. Colors while not required except for special tints may be incorporated if so desired.

Compositions formulated in accordance with the provisions of the present invention provide excellent bonds between the wood and any outer coatings of conventional lacquers, or varnishes which may be applied over the exterior surface thereof. The color imparted by the oil base is highly stable to light. The sealer also penetrates the grain of the wood to a sufilclent degree to inhibit the exposure of unstained surface upon chipping of the coating film. Moreover, the natural grain remains visible while a uniform natural maple-like tone or tint is imparted even to composite bodies containing woods of substantially different grain structures. For this reason the improved sealer is of particular value in coat- I ing cheaper grades of furniture which may be fabricated from a plurality of pieces of wood glued or otherwise joined together to form panels.

Although only a limited number of specific embodiments of the invention have been described,

it will be apparent to those skilled in the art that these are merely exemplary and that numerous modifications may be made therein without departure from the spirit of the invention or the scope of the appended claims.

What I claim is:

1. A composition for sealing and staining surfaces of porous materials comprising a solution of nitrocellulose and a rape seed oil which has been treated by a process consisting in heating it to a a temperature of 500 to 650 F. for a period of 2 to 4 hours.

2. A method of coating wood in order to impart a maple color thereto, which comprises coating it with a mixture of nitrocellulose and a rape seed oil which has been treated by a process consisting in heating it to a temperature of 500 to 650 F. until the color of a 10% solution in xylol approximates that of a 40% solution of gilsonite selects in xylol.

3. A method of coating bodies comprising a plurality of woods of different grain structure in order to impart a uniform maple-like tint thereto 5. A method of forming relatively uniform maple tinted coatings upon bodies formed of woods of a plurality of different grains which comprises applying to the bodies films comprising mixtures of nitrocellulose and rape seed oil has been treated by a process consisting in heating itto a temperature of. about 500 to 600 C. until the oil when in a solution in xylol has about the tint of a 40% solution of gilsonite sewhich lects in xylol, said mixture being dissolved in a m volatile solvent.

- MELVIN W. JOHNSON. 

